The present invention relates to molded packing for intercepting all sorts of fluids which is incorporated in a fluid device used in a nuclear power industry or general industries, and more particularly to easily removable molded packings.
There is conventionally known packing made of only expanded graphite such as GRAPHOIL (manufactured by Union Carbide Co., in U.S.A.). In general industries, such packing is incorporated in the shaft sealing portion, i.e., in the chamber formed by a shaft and a casing of a fluid device such as a valve or pump, thereby to prevent a fluid from leaking to the outside of the device. Such packing made of only expanded graphite is resilient and the characteristics inherent in graphite can be utilized as they are. Thus, such graphite packing is regarded as relatively excellent.
However, such packing produces a high sliding resistance against a member such as a shaft where the packing is installed. Moreover, if the sealing conditions are severe, the packing sticks to the shaft, thus disadvantageously lowering the sealing function of the packing.
Moreover, expanded graphite is in nature fragile, thus requiring care in handling when graphite packing is mounted to the sealing portion of a fluid device. In particular, at the time of replacement of packing for repair or regular checking, the removal of such packing made of only expanded graphite from the shaft sealing portion of a fluid device is extremely difficult and troublesome. Namely, since such packing has been packed with a predetermined fastening pressure, the packing is often held strongly by and rigidly stuck to the shaft sealing portion. Therefore, the removal of such packing from a narrow chamber formed by the shaft and the device casing is extremely difficult. Even if a packing removing means such as a scratch rod is used, the packing is crumbled and the crumbled pieces are merely removed. Accordingly, in order to completely remove the packing from the shaft sealing portion, it is required to disassemble the fluid device. Furthermore, if the shaft sealing portion is frequently scratched with a packing removing means, the shaft or the device casing may be damaged.
In the nuclear power industry, it is of urgent necessity to solve the problem how to shorten the time required to mount and remove the packing, in view of the exposure of workers to radiation.